In turbomachines such as stationary gas turbines or jet engines, air is drawn in along a flow channel, compressed and burned together with fuel in a combustion chamber, a process in which the combustion gases are subsequently expelled via the flow channel in order to drive rotors in a turbine. Moreover, there are guide vanes arranged in the flow channel to guide the fluid. The flow channel with the guide vanes and rotor vanes is completely surrounded by a housing structure which not only is exposed to mechanical loads but which especially also has to ensure that a high temperature difference can be achieved between the fluid in the flow channel and the outside of the housing.
For this purpose, the housing structure can have heat-protection plates and insulation that serve to establish a steep temperature gradient from the flow channel to the outer wall of the housing. In addition, cooling air can be fed into the housing structure in order to dissipate surplus heat.
The state of the art such as, for instance, British published patent application GB 2378730 A has already disclosed such housing structures, which have a cooling-air channel in the immediate vicinity of the inner wall of the housing directly on the flow channel.
U.S. Pat. No. 6,179,557 B1 proposes a cooling procedure entailing a cooling channel whose direction changes, so that cooling air first flows in a first outer part along the direction of flow of the fluid in the flow channel, after which it flows back in the opposite direction and is released into the flow channel. Other housing structures having cooling capabilities are described in international patent application WO 2005/003520 A1, U.S. Pat. No. 6,902,371 B2 and European patent application EP 1106785 A1.